Retrievable bridge plug



Mcl m, w67 R. T. EVANS 3,308,885

RETRIEVABLE BRIDGE PLUG Filed DSC. 26, 1965 3 Sheets-Sheet l INVENTOR.

ROBERT T. EVANS A TTOR NE YS' March 14, 1967 R. T. EVANS RETRIEVABLE BRIDGE PLUG Filed Dec. 26, 1965 42' INVENTOR.

ROBERT T. EVANS BY im@ QM/Mmgw- ATTORNEYS 5 Sheets-Sheet 3 Filed Deo. 26, 1963 INVENTOR.

ROBERT T4 EVANS .1mi QMS. J. S .w ITI- ATTORNEYS' United States Patent 3,308,886 RETRIEVABLE BRIDGE PLUG Robert T. Evans, Duncan, Okla., assignor to Halliburton Company, Duncan, Okla., a corporation of Delaware Filed Dec. 26, 1963, Ser. No. 333,499 14 Claims. (Cl. 166-134) This invention relates to a retrievable bridge plug and, more particularly, to a packer type retrieva'ble bridge plug.

A packer type lbridge plu-g includes packer rings which are expanded against the casing to separate one portion of the well from another. I'he common method of expanding the packer rings is to utilize fluid pressure to provide the force to distort the rings sufficiently for them to engage the well casing. Usually, uid pressure not only expands the packer rings, but also maintains the packer rings in the set position. Fluid pressure differentials for expanding the packer rings are created by O-rings, or other types of seals. Since the seals are exposed to well fluids and high subsurface temperatures, they become deteriorated rapidly and failure of the seals may cause the packer rings to collapse unexpectedly.

Another problem associated with packer type bridge plugs is that a fluid pressure differential acting across the packer rings often causes the packer to be displaced in the casing. Slips may be provided on the bridge plug to resist its displacement, but the slips are actuated in response to the pressure differential on the packer rings. They are in a neutral or non-engaging position when no pressure differential exists. As the pressure diiferential changes from one face of the packer ring to the opposite face, the slips must disen-gage the casing, pass through the neutral position, then engage the casing in the opposite direction. While the slips are moving through the neutral position, the tool is free to move away from its desired position in the well, and therefore it maynotbe at the desired depth when the slips again engage the casing.

Accordingly, it is an object of this invention to provide a retrievable packer type bridge plug which may be set independently of uid' pressure.

It is a further object of this invention to provide a packer type retrievable bridge plug which resists movement relative to the casing after the packer is set.

It is a still further object to provide means for equalizing fluid pressure on opposite sides of the packer ring, before the ring is collapsed.

It is another object to provide a retrievable bridge plug which gives an indicati-on at the surface after the packer is set of whether the tubing string is connected with the tool.

These o'bjects are accomplished in accordance with a preferred embodiment of the invention by a bridge plug having packer rings mounted on a packer mandrel. A control mandrel is telescoped within the packer mandrel and a retrieving head is secured to the upper end of the control mandrel. Slips are mounted in mechanical bodies above and below the packer ring. The upper mechanical slip body is secured on the packer mandrel and the lower mechanical slip body is mounted on the packer mandrel for longitudinal `movement thereon. The lower slips are set first by right-hand rotation and downward movement` of the control mandrel, thereby moving a lug on the control mandrel in a J-slot. This movement of the control mandrel closes ports in the control mandrel above and below the packer rings. Drag springs engage the casing and resist movement of the drag spring sleeve while the control mandrel moves downwardly. At the same time, a lug on the packer mandrel moves out of a locked posi- 3,308,886 Patented Mar. 14, 1967 tion in a J-slot in the drag spring sleeve. The slips move outwardly along an inclined surface on the lower mechanical slip body until they engage the casing. As the control mandrel moves downwardly, -a shoulder on the mandrel engages the upper slip control body, thereby displacing the body downwardly relative to the lower slips. The downward movement of the slip control body moves an inclined surface on the upper mechanical slip body under the upper slips to displace them outwardly against the casing. At this point, t-he upper and lower slips are in engagement with the casing, but the packer rings are not yet expanded.

The downward force which is applied by the control mandrel to the slip control -body causes the slip control body, the upper slips and the upper mechanical slip body to move downwardly. Since downward movement of the lower mechanical slip lbody relative to the casing is resisted by the lower slips which grip the casing, the packer rings are com-pressed axially and expand radially outwardly against the casing. During the expansion of the packer rings, the upper slips slide along the casing wall. The teeth on the slips slope away from the casing toward the packer rings, so lthat they do not bite into the casing until the slips are urged in the upward direction. After the packer rings are expanded, the upper slips bite into the casing to keep the packer rings expanded and to prevent movement of the tool. Continued right-hand rotation of the control mandrel, after the packer rings are expanded, moves the lug on the control mandrel into a locked position in its J-slot. The control mandrel then cannot be moved upwardly.

The lbridge plug is released from the tubing by righthand rotation and upward movement of the tubing string to cause a lug on the retrieving head to move out of the o-pen end of a I-slot in the overshot. An overshot nose on the lower end of the overshot has an internal circumferential ridge. The diameter of the retrieving head plus the length of the lug is slightly greater than the internal diameter of the ridge, so that there is an interference lit between the lug and the ridge. Accordingly, a greater upward pull on the tubing string is required to raise the overshot nose across the lug, thereby serving as an indication at the surface that the bridge plug is set and that the overshot is released.

The control mandrel is provided with radial ports for equalizing fluid pressure in the annular space between the tool and the casing above and Ibelow the packer rings. When the control mandrel is displaced upward relative to the packer mandrel, the ports are opened, but when the control mandrel is displaced downward, the ports are closed, thereby blocking fluid communication through the tool, when the packer rings are set.

This preferred em'bodiment of the invention is illustrated in the accompanying drawings in which:

FIG. l is a schematic elevational view of the retrievable bridge -plug of this invention attached to a tubing string;

FIG. 2 is an elevational View, partially in section, of the top portion of the bridge plug, as indicated in FIG. l;

FIG. 2A is a schematic View of the J-slot in the overshot;

FIG. 3 is an elevational view, partially in section, of the upper intermediate section of the bridge plug, as indicated in FIG. 1;

FIG. 4 is an elevational view, partially in section, of the lower intermediate portion of the bridge plug, as indicated in FIG. l;

FIG. 4A is a schematic view of the J-slot in the drag spring sleeve;

FIG. 5 is an elevational view, partially in section, of the bottom portion of the bridge plug, as indicated in FIG. 1;

FIG. 5A is a schematic view of the control I-slot in the J-slot body;

FIG. 6 is an enlarged cross sectional detail view of one of the upper slips;

FIG. 7 is a cross sectional View of the top portion of the bridge plug, after the packer rings have been set in a well casing; i

FIG. 8 is a cross sectional view of the upper intermediate portion of the bridge plug, after the packer rings have been set; Y,

FIG. 9 is a cross sectional view of the lower intermediate portion of the bridge plug, after the packer rings have -been set; and

FIG. 10 is a cross sectional view of the bottom portion of the bridge plug after the packer rings have been set.

VThe retrievable bridge plug is attached to a coupling 2 on the end of a tubing string. An overshot 4 has internal screw threads 6 which cooperate with the threads on the coupling 2 to secure the overshot 4 to the -coupling 2. A retrieving head 8 is telescoped in the overshot 4 and a lug 10 on the retrieving head cooperates with an internal J-slot 12 in the overshot 4 to control the position of the retrieving head 8 relative to the overshot. An overshot nose 14 is secured to the lower end of the overshot. 'The nose 14 has a ridge 16 extending around the interior wall of the nose. The diameter of the retrieving head plus the length of the lug 10 is slightly greater than the internal diameter of the ridge 16, thereby forming an interference t therebetween. The wall of the nose 14 has a plurality of slots 17 which allow the nose to expand slightly as the lug 10 is forced over the ridge 16. The retrieving head is secured by screw threads to the upper end of a control mandrel 18. The mandrel 18 extends downward from the retrieving head 8 to the lower end of the bridge plug.

A slip control body 20 is telescoped over the control mandrel 18 and relative movement between the body 20 and the mandrel 18 is controlled by a cylindrical recess 22 in the body 20. A ycollar 24 on the mandrel 18 is movable in the recess 22. At the lower end of the-body 20, an upper slip retainer ring 26 is secured to the body 20 by screw threads. A junk catcher 28 is also threadedly secured on the slip control body 20 and a resilient cup 30 is clamped between the junk catcher 28 and the slip retainer ring 26 to prevent sand settlement around the upper slip assembly.

The slip retainer ring 26 has a plurality of T-slots 32 spaced around the circumference of the ring 26 and upper slips 34 each have one end mounted in one of the T-slots 32. The lower end of each slip 34 has lateral anges for cooperating with inclined T-slots 36 in a mechanical slip body 38. The T-slots 36 slope downwardly, so that upon downward movement of the slips 34, they will move outwardly in the slots 32 and 36. The upper mechani- V cal slip body'38 is movable longitudinally along the control mandrel 18 and is threadedly secured to a packer mandrel 40. A plurality of packer rings 42 and spacer rings 44 are mounted on the mandrel 40 for sliding movement relative thereto. A spacer ring 46 is also threaded on the mandrel 40 between the slip body 38 and the first packer ring 42. A lower mechanical slip body 48 on the mandrel 40, having a spacer ring 50 secured thereto, is movable upwardly along the mandrel 40. A shoulder S2 on the mandrel 40 prevents downward displacement of the body 48 relative to the mandrel and facilitates retraction of the lower slips. A plurality of slips 54 are spaced around the circumference of the packer mandrel 40 and each slip has one end mounted in one of the inclined T-slots 56 formed in the lower mechanical slip body 48. The slips are retained in their respective T-slots 56 by lateral flanges on opposite sides of the slips. A split ring collar 58 having T-slots 60 formed therein is mounted on the packer mandrel 40 below the slips 54 'andn the opposite end o'feach lower slip 54 is mounted in one of the T-slots 60.A A drag spring sleeve 62 is mounted on the packer mandrel 40, as shown in FIG. 4, and the collar 58 extends over a ilange 64 on the sleeve 62, so that the collar 58 and the sleeve 62 are connected together. Drag springs 66 having their opposite ends secured in the sleeve 62 are bowed outwardly to eng-age the walls of the casing.V A .I-slot 68, as shown in FIG. 4A, is formed in the sleeve 62 and a lug 70 formed on the packer mandrel 40 extends radially outward through the J -slot 68.

A bypass body 72 is threadedly secured to the ylower end of the packer mandrel 40 and has a port 74 therein. The control mandrel 18 has bypass ports for providingy fluid communication above and below the packer rings. There is a lower bypass port 76 in the control mandrel 18 in alignment with the port 74, as shown in FIG. 5. Other bypass ports 78 and 80 are located in the control mandrel above the packer rings 42. When the control mandrel 18 is displaced downward, O-rings cooper-ate with the mandrel to prevent leakage of duid through the ports 76 and 80. A pair of O-rings 82 are mounted in the mechanical slip body 38 to form a seal .for the port 80. The port 76 is sealed between two pairs of O-rings 84 and 86, when the mandrel 18 is displaced downward.

A J -slot body 88 is threadedly secured to the lower end of the bypass body 72. rl`he J-slot body 88 is provided with a J-slot 90 having the shape shown in FIG. 5A. A lug 92 on a mandrel cap 94, which is secured to the lower end of the control mandrel 18, cooperates with the J-slot 90 to control the relative position of the mandrel 18.

As shown in FIG. 6, the upper slips y34 have teeth 96 thereon for gripping the well casing. The teeth slope upwardly away from the packer rings. Therefore, the teeth on the slipsV 34 may slide downwardly along the casing, but movement in the upward direction causes the teeth to'become wedged against the casing.V The teeth may be individual segments of a hard material, such as tungsten carbide, to avoid damaging the teeth as they are sliding along the casing. The tooth segments may be set into the slip and cemented in place.

FIGS. 7 to 10 show the tool as it is set in a casing, which is shown schematically at 98. When the packer is loweredv into a well, the ports 76, 78 and 80 communicate between the interior of the control mandrel 18 and the annular space between the packer tool and the casing. When the desired depth -for setting the packer rings is reached, the rn-andrel 18 is given a suflicient right-hand rotation to move the lug 92 out of the short upper portion of the J-slot 90, as shown in FIG. 5A, to the long portion of the J-slot. TheV drag springs 66, which engage the Vcasing, resist movement of the sleeve 62 and, while the lug 92 is moving into the long portion of the J-slot 90,- the lug 70 on the packer mandrel 40 moves into the: long portion of the .l -slot 68. A downward force is then; applied to the tubing string to displace the control mandrel 1S downwardly relative to the sleeve 62. The downward force is transmitted through the retrieving head v lugv10 which engages the top of the J-slot 12 in thel overshot 14. When the control mandrel 18 is displaced downwardly, iuid communication through the ports 76 and is blocked by the respective O-rings 82, 84 and 86. When the mandrel 18 moves downward relative to the sleeve 62, the lower end of the retrieving head 8 engages the slip control body 20 and the force is transmitted to the packer mandrel 40. Downward displacement of the packer mandrel 40 and the lower mechanical slip body 48 relative to the drag spring sleeve 62 causes the lower slips 54 to move outwardly along the inclined T-slots 56 until the slips engage the casing 98, as shownV in FIG. 8. After the lower slips engage the casing, the lower mechanical slip body 48 is blocked from :further downward movement by the slips 54 which are wedged against the casing.

The upper slips 34 are then expanded by the further application of force to the tubing string. The force is transmitted to the slip control body 20 through the retrieving head 8 for displacing the slip retainer 26 downward, thereby causing the slips 34 to ride outwardly along the inclined T-slots 32 and 36. The slips move outwardly until they engage the casing. Since the lower slips 54 are wedged against the casing, continued downward movement of the slip control body 20 axially compresses the packer rings 42 until they expand radially into engagement with the casing. The upper slips 34 slide downwardly along the casing with the upper mechanical slip body 38 while the packer rings are being expanded. The angular orientation of the teeth 96 on the upper slips 34 permits the slips to slide downwardly along the casing, but when the downward movement stops, the resiliency of the packer rings 42 urges the slips 34 upwardly and the teeth 96 are wedged into the surface of the casing, thereby resisting upward displacement of the slips. The wedging action of the upper and lower slips not only maintains the packer rings expanded, but also prevents vertical movement of the packer rings relative to the casing. The control mandrel 18 is locked in its downwardmost position by right-hand rotation of the tubing string, which moves the lug 92 into the lower short section of the J-slot 90, as shown in phantom lines in FIG. 5A.

The tubing string may be released from the tool by right-hand rotation and upward movement of the tubing string, which moves the lug 10 on the retrieving head 8 into the open end of the J-slot 12 in the overshot 4. The interference t between the ridge 16 in the nose 14 and the lug 10 requires an upward pull of suflicient magnitude to indicate at the surface when the lug 10 has passed over the ridge and the overshot 4 is Ifree from the remainder of the tool.

To collapse the packer rings and retrieve the tool, the overshot 4 is lowered over the retrieving head 8 and the lug 10 is cammed into the I-slot 12. The weight of the tubing string is slacked off until the lug 10 moves over the ridge 16. The shape of the J-slot 12 causes the lug 10 to be cammed into the short closed section of the I- slot, as shown in FIG. 2A. Downward movement of the control mandrel 18 moves the pin 92 out of the lower hooked section of the J-slot 90, as shown in FIG. 5A, and left-hand rotation of the mandrel 18 moves the pin 92 into the straight portion of the I -slot. Upward movement of the mandrel 18 then opens the bypass ports 76, 78 and 80, to equalize the fluid pressure above and below the packer rings. Continued upward movement of the tubing string causes the collar 24 to engage the shoulder at the upper end of the recess 22 in the slip control body 20. Upward movement of the slip control body 20 pulls the slips 34 away from the casing 98. This is done 'easily, since the pull is directly on the slips 34 and the wedge angle of the slips and the T-slot 36 in the slip body 38 is a relatively large angle. A small longitudinal movement of the slips will retract the slips inwardly enough to disengage them from the casing. After the upper slips are disengaged from the casing,- the packer -rings 42 are free to retract by their own resilience. While the tubing string is moving upwardly, the :pin 70 is cammed into the short section of the I-slot 68 and the lug 92 is moved to the upper short section of the I-slot 90. The upward movement of the control mandrel 18 is then transmitted to the packer mandrel 40 and the shoulder 52 moves the lower mechanical slip `body 48 upwardly to draw the lower slips 54 inwardly. The tool may then be removed from the well, or moved to another position in the well.

This retrievable bridge plug is an improvement over other retrievable bridge plugs now in use in that the packer rings are maintained in the sealing position by two opposing sets of mechanical slips, which positively engage the casing. Other retrievable bridge plugs depend upon internal fluid pressure retained by resilient seals which are subject to deterioration by well iluids or by high subsurface temperatures. lFurthermore, the two sets of opposing slips engage the casing at all times and there can be no movement of the tool or the slips as pressure reversals occur in the well. Since the bridge plug is mechanically set by the application of downward weight to the tool, its operation is not dependent upon well uids, or the lack of such fluids.

While this invention has been illustrated and described in one embodiment, it is recognized that variations and changes may be made therein, without departing from the invention as yset forth in the claims.

1. A retrievable bridge plug comprising a packer mandrel, a packer ring mounted on said mandrel, a plurality of upper slips and lower slips on opposite sides of the packer ring, said slips being Imounted in mechanical slip bodies, -said packer ring being positioned between and in engagement with said mechanical slip bodies, each of said 'bodies having a shoulder adjacent the packer ring and having inclined surfaces cooperating with said slips to displace said slips outwardly against a well casing upon longitudinal movement of said slips relative to said slip bodies, one of said bodies being movable longitudinally along the mandrel, the other of said bodies being secured to said mandrel, and means for moving said one body toward the other body and said slips longitudinally toward each other and longitudinally relative to their respective mechanical slip bodies to expand the packer ring, wherebythe slips maintain the packer ring expanded.

2. A retrievable bridge plug according to claim 1, wherein said moving means includes a control mandrel mounted for axial movement in said packer mandrel, said control mandrel having shoulder means thereon in position to displace said slips relative to said other slip body.

3. A retrievable bridge plug according to claim 2 Wherein said slips have teeth projecting outwardly therefrom, said teeth being angularly disposed and having a greater slope on the side opposite the packer ring, whereby the slips may be displaced longitudinally toward said packer ring while engaging a well casing, but resist movement away from said packer ring.

4. A retrievable bridge plug according to claim 3 wherein said slips have teeth formed of individual segments secured therein, said upper slip teeth sloping in a direc tion opposite to that of said lower slip teeth.

5. A retrievable bridge plug comprising a hollow control mandrel, means mounting a packer ring on said mandrel, means on the mandrel for expanding the packer ring against a well casing upon longitudinal movement of said mandrel in one direction, said expanding means including abutments on opposite sides of said packer ring, said abutments being movable toward each other to expand said packer ring outwardly by axially compressing said ring therebetween, and means on the mandrel adjacent to the packer ring for gripping the casing, said .control mandrel having radial ports therein above and below the packer ring, said control mandrel being movable longitudinally of said ring expanding means and cooperating with said expanding means upon movement of said mandrel in said one direction to close the ports when the packer ring is expanded, said mandrel being movable longitudinally relative to said expanding means in a direction opposite to said one direction while said packer ring is expanded to open said ports, whereby iluid pressure on opposite sides of the packer ring is equalized before the packer ring is collapsed.

6. A retrievable bridge plug comprising a control mandrel, a packer mandrel mounted in telescoping relation on the control mandrel, a packer ring mounted on the packer mandrel, an upper slip mechanical body secured to the packer mandrel, a lower slip mechanical body mounted on the packer mandrel and movable longitudinally thereof, slips attached individually to said upper and said lower mechanical bodies, said mechanical bodies having inclined cam surfaces cooperating with cam surfaces on said slips, drag springs, means mounting the drag springs on the packer mandrel, said drag spring mounting means being movable selectively longitudinally of the packer mandrel for camming the lower slips outwardly against a well casing, said control mandrel having means thereon for moving sequentially said mechanical bodies to displace the slips outwardly upon axial movement of the control mandrel, and means for selectively locking said control mandrel after said axial movement, whereby the packer ring and the slips are expanded against the well casing and maintained in the expanded condition.

7. A retrievable bridge plug comprising a control mandrel, a packer mandrel mounted in telescoping rel-ation on the control mandrel, a packer ring mounted on the packer mandrel, an upper slip mechanical body secured to the packer mandrel, a lower slip mechanical body mounted on the packer mandrel and movable longitudinally thereof, slips attached Vat one end individually to said upper and said lower mechanical bodies, said mechanical bodies having opposed shoulders inclined cam surfaces cooperating with cam surfaces on said slips, said .packer ring being positioned between said opposed shoulders, a drag spring sleeve having drag springs thereon, said sleeve being mounted coaxially on the packer mandrel below said lower mechanical body, said lower slips being attached at the opposite end of said sleeve, said drag spring sleeve and said packer mandrel including first I -slot means therebetween for limiting relative axial movement in one rotational position and permitting relative axial movement in a second rotational position, said control mandrel and said packer mandrel including second J-slot means therebetween for limiting relative laxial movement in one rotational position and permitting axial movement in a second rotational position, thereby selectively camming said lower slips outwardly upon relative rotation of said sleeve and packer mandrel to said second rotational position and subsequently camming said upper slips outwardly upon downward axial movement of the control mandrel, said second J-slot means being in said one rotational position during said control mandrel axial movement and being in said second rotational position when said upper slips are displaced outwardly, thereby locking the slips and packer ring in expanded position.

8. A retrievable bridge plug according to claim 7 wherein said control mandrel includes a shoulder, said shoulder being spaced longitudinally above said upper slips, whereby said packer mandrel moves longitudinally in one direction relative to the sleeve to set the lower slips before said control mandrel shoulder displaces said upper slips against a well casing. v

9. A retrievable bridge plug according to claim 8 wherein said second J -slot means includes a I -slot formed 'm one of said mandrels and a lug on the other of said mandrels and extending into said I-slot, said J -slot having a hook portion at the lower end thereof, whereby engagement of the lug in the hook portion prevents relative axial movement of the mandrel in response to the resilience `of the compressed packer ring.

' 10. A retrievable bridge plug according to claim 8 wherein said slips have teeth thereon, said upper slip teeth being inclined in a direction opposite that of said lower slip teeth, said control mandrel having a second shoulder for drawing said upper slips away from the well casing upon upward longitudinal movement of said control mandrel in a direction opposite to said one direction.

11. A retrievable bridge plug according to claim 10 wherein said control mandrel has an upper .port and a lower port, said packer mandrel having a port below said Vpacker ring, said packer mandrel port being aligned with said control mandrel lower port when-said lower slips are retracted and when said control mandrel is displaced in said opposite direction, and said port being misaligned 8 when said controlmandrel is displaced in said one direction relative to said packer mandrel, whereby the ports are closed during setting of the packer ring and reopened before collapse of the packer ring.

12. A retrievable bridge plug comprising a mandrel, a packer ring, means mounting the packer ring on the mandrel, upper and lower slips on opposite sides of the packer ring, means for mounting the slips on the mandrel, said mounting means including inclined surfaces cooperating with said slips to displace said upper and lower slips outwardly from said mandrel, means on said mandrel for v displacing said upper and lower slips longitudinally toward said packer ring and relative to said mounting means for expanding said slips outwardly upon longitudinal movement of the mandrel in one direction, said mounting means including upper and lower abutments adjacent said packer ring, said abutments being movable toward each other upon longitudinal movement of the mandrel in said one direction for radially expanding the packer ring therebetween, and J-slot means on said mandrel for locking said mandrel independently of said slips after said longitudinal movement relative to said slip mounting means, whereby the slips and packer ring are maintained expanded.

13. A retrievable bridge plug comprising a control mandrel, a packer mandrel, a packer ring mounted on the packer mandrel, an upper slip mechanical body secured to the packer mandrel, a lower mechanical slip body mounted on the packer mandrel movable relative thereto, upper slips, means mounting the upper slips on the packer mandrel, lower slips, means mounting the lower slips on the packer mandrel, said upper and lower mechanical slip bodies having opposed shoulders and inclined cam surfaces thereon cooperating with inclined surfaces on the slips for expanding the slips against a well casing upon longitudinal displacement thereof, said packer ring being positioned between said opposed shoulders, a drag spring sleeve having drag springs thereon, said spring sleeve being mounted in coaxial relation on said packer mandrel, one of said slip mounting means being secured on said spring sleeve and the other of said slip mounting means being secured on said packer mandrel, first I-slot means for selectively displacing said control -mandrel and said packer mandrel longitudinally in one direction relative to the drag spring sleeve, second J -slot means for selectively displacing said control mandrel longitudinally in said one direction relative to the packer mandrel, said control mandrel having ports therein communicating above and below the packer ring, means on said packer mandrel forming a valve for said control mandrel ports, said valve means being in position for closing said ports upon longitudinal displacement of the control mandrel in said one direction whereby when said control mandrel is displaced in said one direction in sequence, the ports are closed, the upper slips are expanded against the well casing, the lower slips are expanded against the well casing, and the packer ring is compressed by the mechanical slip bodies until it extends radially outward to engage the well casing.

14. A retrievable bridge plug comprising a control mandrel, a packer mandrel, a packer ring mounted on the packer mandrel, an upper slip mechanical body secured to the .packer mandrel, a lower mechanical slip body mounted on the packer mandrel movable relative thereto, upper slips, means mounting the upper slips on the packer mandrel, lower slips, means mounting the lower slips on lthe packer mandrel, said upper and lower mechanical slip bodies having opposed shoulders and inclined cam surfaces thereon cooperating with inclined surfaces on the slips for expanding the slips against a well casing upon longitudinal displacement thereof, a drag spring sleeve having drag springs thereon, said sleeve being mounted coaxially on said packer mandrel, one of said slip mounting means being secured on said'spring sleeve and the other of said slip mounting means being secured on said packer mandrel, first I-slot means for selectively dis-placing said packer mandrel in one direction relative to the sleeve, said lower slips being mounted at one end on said sleeve, said sleeve restricting axial movement of such lower slips relative to said sleeve and permitting radial movement of said lower slips relative to said sleeve, thereby expanding said lower slips independently of said upper slips upon movement of said packer mandrel in said one direction, means on the mandrel for displacing said upper slips longitudinally relative to said upper slip body, said displacing means including an upper slip retaining sleeve on said mandrel and movable toward said upper mechanical slip lbody to expand said upper slips, and `means for selectively moving said slip retaining sleeve toward said upper mechanical slip body, whereby the upper slips slide along the casing to expand the packer.

References Cited by the Examiner UNITED STATES PATENTS Young 166-134 Lockwood 166-240 Smith 166-138 Lynes 166-150 Stevenson 294-86.1 Shelner 294-861 Miller 166--182 Brown 166--134 CHARLES E. OCONNELL, Primary Examiner.

J. A. LEPPINK, Assistant Examiner. 

1. A RETRIEVABLE BRIDGE PLUG COMPRISING A PACKER MANDREL, A PACKER RING MOUNTED ON SAID MANDREL, A PLURALITY OF UPPER SLIPS AND LOWER SLIPS ON OPPOSITE SIDES OF THE PACKER RING, SAID SLIPS BEING MOUNTED IN MECHANICAL SLIP BODIES, SAID PACKER RING BEING POSITIONED BETWEEN AND IN ENGAGEMENT WITH SAID MECHANICAL SLIP BODIES, EACH OF SAID BODIES HAVING A SHOULDER ADJACENT THE PACKER RING AND HAVING INCLINED SURFACES COOPERATING WITH SAID SLIPS TO DISPLACE SAID SLIPS OUTWARDLY AGAINST A WELL CASING UPON LONGITUDINAL MOVEMENT OF SAID SLIP RELATIVE TO SAID SLIP BODIES, ONE OF SAID BODIES BEING MOVABLE LONGITUDINALLY ALONG THE MANDREL, THE OTHER OF SAID BODIES BEING SECURED TO SAID MANDREL, AND MEANS FOR MOVING SAID ONE BODY TOWARD THE OTHER BODY AND SAID SLIPS LONGITUDINALLY TOWARD EACH OTHER AND LONGITUDINALLY RELATIVE TO THEIR RESPECTIVE MECHANICAL SLIP BODIES TO EXPAND THE PACKER RING, WHEREBY THE SLIPS MAINTAIN THE PACKER RING EXPANDED. 